Unless bot AI is recoded at a very fundamental level, this isn't likely to be possible. Bots always face their nearest threat/mass of the enemy...it simply isn't possible to have them face other directions without repeatedly knocking them out of an alarmed/battle-ready state. Likely the same reason you don't see any orders for bots to form battle squares and the like. It would take reworking the engine's handling of bots, targeting, etc that could have unforeseen consequences--like ranged units facing away from the enemy--or very hacky modder-level attempted workarounds that probably wouldn't have particularly good results.